U.S. patent number 4,852,578 [Application Number 07/118,993] was granted by the patent office on 1989-08-01 for rapidly quantifying the relative distention of a human bladder.
This patent grant is currently assigned to The United State of America as represented by the Administrator of the. Invention is credited to Travis N. Blalock, Albert R. Cavalier, John A. Companion, Joseph S. Heyman, Beth A. Mineo.
United States Patent |
4,852,578 |
Companion , et al. |
August 1, 1989 |
Rapidly quantifying the relative distention of a human bladder
Abstract
A device and method rapidly quantifying the relative distention
of the bladder of a human subject are disclosed. Ultrasonic
transducer 1, which is positioned on subject 2 in proximity to
bladder 16, is excited by pulser 3A under command of microprocessor
4 to launch an acoustic wave into patient 2. This wave interacts
with bladder walls 12,13 and is reflected back to ultrasonic
transducer 1, when it is received, amplified and processed by
receiver 3B . The resulting signal is digitized by
analog-to-digital converter 5 under command of microprocessor 4,
and is stored in data memory 6B. The software in microprocessor 4
determines the relative distention of bladder 16 as a function of
the propagated ultrasonic energy; and based on programmed
scientific measurements and individual and anatomical and
behavioral characteristic of with the specific subject as contained
in program memory 6A, sends out a signal to turn on any or all of
the audible alarm 7, the visible alarm 8, the tactile alarm 9 , and
the remote wireless alarm 10.
Inventors: |
Companion; John A. (Hampton,
VA), Heyman; Joseph S. (Williamsburg, VA), Mineo; Beth
A. (Arlington, TX), Cavalier; Albert R. (Arlington,
TX), Blalock; Travis N. (Knoxville, TN) |
Assignee: |
The United State of America as
represented by the Administrator of the (Washington,
DC)
|
Family
ID: |
26816953 |
Appl.
No.: |
07/118,993 |
Filed: |
November 10, 1987 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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929869 |
Nov 13, 1986 |
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Current U.S.
Class: |
600/449 |
Current CPC
Class: |
A61B
5/204 (20130101); A61B 8/08 (20130101); A61B
8/0858 (20130101) |
Current International
Class: |
A61B
8/08 (20060101); A61B 5/20 (20060101); A61B
010/00 () |
Field of
Search: |
;128/661.03
;73/596-600,602 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Wells, P. N. T. "Ultrasonics in Clinical Diagnosis", Churchill
Livingston, N.Y. 1977, pp. 148-151. .
Mortimer, A. J. et al., "System for Histogram Production in
Automatic Midline Echoenceephalography", MBEC vol. 15, 1977, 1977
pp. 78-80. .
Ostro, P. et al., "Digital UTS Image Processing w/Microprocessor
Manipulation". .
Jrnl. of Med. Engrg. & Technology, vol. 2 #5, (Sept. 1978) pp.
234-238. .
Hoshino, H. et al., "Microprogrammable UTS Image Processor", SPIE
vol. 314, DIG. Radiography (1981) pp. 354-361..
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Primary Examiner: Jaworski; Francis
Attorney, Agent or Firm: Helfrich; George F. Manning; John
R. Glenn; Charles E. B.
Government Interests
ORIGIN OF THE INVENTION
The invention described herein was jointly made: in the performance
of work under a U.S. Department of Education/National Institute for
Handicapped Research grant to the Association for Retarded Citizens
of the United States, and is subject to the provisions of the
Education Department General Administrative Regulations, revised
July 1, 1985: and in the performance of work under a NASA Contract,
and is subject to the provisions of Section 305 of the National
Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat. 435:
42 USC 2457).
Parent Case Text
This application is a continuation-in-part of co-pending
Application Ser. No. 06/929,869, filed Nov. 13, 1986 and now
abandoned.
Claims
What is claimed as new and desired to be secured by Letters Patent
of the United States is:
1. A device for rapidly quantifying the relative distention of the
bladder of a human subject, which device comprises:
ultrasonic transducer means for positioning on the external abdomen
of the subject in proximity to the bladder, for the purpose of
launching acoustic waves into the subject followed by receiving
reflected acoustic waves from the subject:
pulser/receiver means communicating with a source of power and the
ultrasonic transducer means for exciting the ultrasonic transducer
means to launch the acoustic waves and for amplifying and
processing the reflected waves received by the ultrasonic
transducer means, and for providing analog signals representative
of at least one reflected ultrasonic waveform over a respective
time interval;
converter means communicating with the pulser/receiver means for
digitizing the analog signal from the pulser/receiver means to
provide a corresponding digital signal representative of said at
least one waveform:
memory means communicating with the converter means for storage of
the digital signal therefrom;
input means for providing a digital input signal representative of
a characteristic of said subject related to the relative distention
of the bladder: and
logic means communicating with the pulser/receiver means for
commanding excitation of the ultrasonic transducer means the logic
means communicating additionally with the converter means for
commanding the digitization of the analog signals from the
pulser/receiver means; the logic means communicating additionally
with the memory means for receiving said digital input and said
stored signals for processing said stored signals to provide a
function signal related to the value of the digitized signals and
their time of occurrence within said respective time intervals, and
for comparing said function signal with said digital input signal;
thereby quantifying the relative distention of the bladder of the
human subject as a function of the propagated ultrasonic
energy.
2. The device of claim 1, which additionally comprises alarm means
communicating with the logic system to alert the subject when the
relative distention of the bladder has reached a given level.
3. The device of claim 2, wherein the alarm means is adapted to be
placed on or in proximity to the subject and is selected from the
group consisting of audible alarm means, visual alarm means, and
tactile alarm means.
4. The device of claim 2, wherein the alarm means is adapted to be
employed remotely from the subject and is selected from the group
consisting of audible alarm means, visual alarm means, and tactile
alarm means.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to the rapid signature analysis
characteristic of changes in an elastic membrane caused by stress,
as a function of energy transmitted into the membrane and reflected
therefrom. It relates particularly to a device for rapidly
quantifying the relative distention of the bladder of a human
subject as a function of ultrasonic energy transmitted into the
subject and reflected therefrom.
There has been a long standing need for a device for rapidly
quantifying the relative distention of bladders of human subjects,
especially the mentally retarded, the infirm, the elderly and those
with quadriplegia.
In attempts to normalize the lives of persons with mental
retardation, much energy has been devoted to teaching these persons
how to function independently in society. The problem of
incontinence often thwarts the best of these efforts while
sophisticated toilet training programs are quite successful in
teaching some persons what to do once the internal sensation of a
full bladder is perceived, these programs typically presuppose that
a person is capable of realizing when she/he has to void. The
subset of the population of persons with mental retardation for
whom continued incontinence is a more common problem are those
persons with severe or profound mental retardation, i.e., those
with IQs less than 35 and significant deficits in adaptive
behavior, who have difficulty in recognizing the subtle and
somewhat obscure signals of their bladders.
In addition, there is a substantial need to provide increased
independence for persons who have permanently lost the ability to
control their bladders for medical reasons such as diabetes,
cerebral palsy, quadriplegia, spina bifida, and advanced age.
Incontinence typically results in a stigma for the person, reduced
positive interaction with other people, unsanitary living
conditions, excessive laundry expenses, and increased custodial
attention by caregivers. Because of the failure to acquire
fundamental toileting skills, such persons are often excluded from
a wide variety of vocational, social, and recreational programs, in
addition to many preschool programs--all of which are important
components of overall experience necessary for their developmental
growth and eventual integration into community life.
Previous attempts to employ technology in urinary toilet training
fall into two classes. The first class is the wetness detector,
which alerts the subject when urine is present on the person. A
particular example of this is the employment of a
moisture-sensitive apparatus in the clothing or in the bed, which
device triggers an alarm when moisture is detected. The second
class is the motion-sensitive device, which is located in the
toilet. Once/voiding has begun, the motion imparted to this device
triggers an alarm which helps the user recognize that urination has
been initiated. However, both classes of devices produce their
effects after urination has taken place. That is to say, their
users are helped to recognize when voiding has been initiated, but
they are not helped to recognize the preliminary need to urinate,
and thereby make the association between this need and
socially-acceptable toileting behavior. In neither case is there a
quantification of the relative distention of the bladder, which
would be of significance in helping one to recognize the
preliminary need to urinate.
Urologists have recently employed an ultrasonic device which scans
the entire bladder and images it with a sector scan to show the
extent of the bladder wall over a sixty degree angle. Other
recently-developed devices are based on an ultrasonic "A" scan
technique , using the time of flight of the sound wave between the
front and back walls. These devices are typically bulky and
expensive. Moreover, even the most sophisticated of the current
devices suffers from inaccuracies resulting from the assumption of
a simple, usually spherical, shape for the bladder. In actuality,
the bladder is not a sphere, rectangle, or other simple geometric
shape. It varies in shape continuously as it fills, varies in shape
as between individuals, varies in height relative to the pelvic
girdle as between the sexes, and if it ever did approach the point
of becoming a sphere, hyperdistention would be imminent.
While 50 cc of urine is considered to be a significant void volume,
void volumes in test subjects varied from 30 cc up to over 1000 cc.
The test population to date has tended to void between 180 and 400
cc. The subject's perception is of increasing discomfort above
approximately 200 cc. In individuals with urinary disfunction the
bladder has been inflated through a catheter to upward of 600 cc
with no real sensation being reported.
It is therefore a primary object of this invention to provide a
device for the quantification of the relative distension of the
urinary bladder of a human subject over a wide range of volumes,
and with greater accuracy than any non-scanning ultrasound device
available from the prior art.
A further object of this invention is to provide adaptability to
the requirements of a human subject in a user selectable manner,
thereby mimicking normal perception and affording help to the
subject in recognizing the appropriate tide to urinate. Since an
intended application of the present invention is for individuals
experiencing bladder dysfunction for varying reasons and at varying
ages, an adaptable operating system is a must. A microprocessor
based design, with as much as possible of the functionality of the
device in software, is indicated.
A further object of this invention is to provide a device for
rapidly quantifying the relative distention of the bladder of a
human subject, thereby providing vital information needed by the
subject during the critical time when the bladder is at or near its
full extension, and affording help to the subject in recognizing
the preliminary need to urinate.
Other objects and advantages of this invention will become apparent
in the specification and drawings which follow.
SUMMARY OF THE INVENTION
The present invention comprehends the provision of an ultrasonic
transducer, which is positioned in proximity to the abdomen of the
subject under test, for the purpose of transmitting energy in the
form of acoustic waves into the bladder of the subject followed by
receiving acoustic waves reflected from the bladder of the subject.
A pulser/receiver communicates with a source of power and the
transducer and excites the transducer to transmit energy in the
form of acoustic waves. It also amplifies and processes the
reflected acoustic waves received by the transducer and provides
analog signals representative of at least one reflected ultrasonic
waveform over a respective time interval. A converter communicates
with the pulser/receiver to digitize the analog signal from the
pulser/receiver to provide a corresponding digital signal
representative of at least one waveform. A memory communicates with
the converter for storage of the digital signal from the converter.
An input means provides a digital input signal representative of a
characteristic of the subject related to the amount of urine in the
bladder. A logic system communicates with the pulser/receiver to
command excitation of the ultrasonic transducer. The logic system
communicates additionally with the converter to command
digitization of the analog signals from the pulser/receiver. The
logic system also communicates with the memory to receive the
digital input and the stored signals for processing the stored
signals to provide a function signal related to the value of the
digitized signals and their time of occurrence within the
respective time intervals, and for comparing the function signal
with stored, preselected function levels to determine equivalency
and to activate a preselected alarm upon the attainment of
equivalency. The relative distention of the bladder of the human
subject is thereby rapidly quantified.
According to the present invention, an ultrasonic transducer is
placed in contact with the skin of the subject on the midline, just
above the pubic symphysis. The transducer is coupled to the skin by
means of a medically approved, water-based couplant. The transducer
serves as both pulser and receiving element in the pulse-echo
system. An analog to digital converter processes the amplified echo
return and supplies eight bit amplitude data, in a histogram
format, to a controlling microprocessor. All control functions are
contained in EPROM or are selectable from front panel BCD
switches.
The genesis of this device was the need for an inconspicuously
small, battery operated monitor that could be worn by an individual
during the course of normal activities. The device should be
adjustable by the individual in areas such as setting the
appropriate volume level for the alarm to be given, and the type,
intensity, and duration of the alarm. Further, variations of the
programming should be selectable, including a setup mode to assist
in proper positioning of the transducer, as well as slightly
different versions of the program to optimize the signal processing
for individuals of different body sizes and configurations.
In the interests of mechanical, electrical and fiscal simplicity,
an "A" scan format was chosen. The signal processing differs from
the prior art as used in other "A"scan based instruments, which,
even were they to be reduced to a comparable size, would suffer
from inaccuracies in the interpretation of the "A" line scan,
related to the non-symmetric mode of expansion of a real
bladder.
From Grey's Anatomy the depiction of the bladder shows an organ
that is well above the pelvic basin and with the major axis roughly
parallel to the abdominal surface in infancy. As the individual
ages, the bladder sinks toward the pelvis. In the female, probably
beginning at puberty, the bladder is typically lower than in the
male. As the bladder slides down and back over time into the
pelvis, the major axis becomes more horizontal. In both the
transverse and sagittal sections the bladder is roughly triangular,
until some degree of distention is arrived at. The progress of fill
of the bladder is as follows: the cavity of the empty bladder takes
the shape of a flattened "Y", with the urethra at the bottom. This
is true in both the fore-aft plane and the lateral plane. The "Y"
gradually fills to the top and then the actual expansion begins.
The bladder expands in the fore-aft plane, and in the vertical
plane, giving rationale for the front-wall to back-wall time of
flight measurements. However, as will be delineated hereinafter,
the non-symmetric expansion of the bladder limits both the dynamic
range and the overall accuracy of a strictly time-based system.
In the information content of any ultrasound scan into the abdomen,
there are a number of givens: the transmitted pulse and its
associated decay will be present, the transducer-skin interface
will produce an echo, the skin to underlying muscle will produce an
echo, and the muscle to abdominal cavity interface will produce an
echo. These echoes will always be present in the early portion of
the return, on all subjects. At low levels of inflation, the front
wall of the bladder is a poor target. It is a rounded point in the
transverse section and even more acute in the sagittal section.
There is no single true diameter. To compound the problem, as the
bladder expands, while it does become a better target, the front
wall also moves toward and eventually merges with the ever present
abdominal wall echoes at the front of the returning echo. All of
this makes the front wall, for much of the range of bladder
expansion, a poor marker. All of this does not negate the value of
time of flight measurements, however, as the back wall will remain
in view, and the transducer itself can serve as the first
marker.
The time of flight measurement, however, has an additional
deficiency-- lack of dynamic range. If the bladder were expanding
in a vacuum, this would not be the case. In the body, however, the
bladder soon runs out of room to expand to the rear, the sides and
the front. Taking the path of least resistance, the primary
direction of expansion in the upper ranges of volume is vertical,
lifting and displacing the intestines. Movement in individuals who
have had major abdominal surgery can produce some interesting
vectors.
An additional factor that has a bearing on the analysis of data
derived from an "A" line scan is that the movement of the back wall
of the bladder, other than in very young children, is not a direct
translation, but rather the elevation of the angle of a curved
surface relative to the axis of the insonating beam. Further, as
this surface becomes more perpendicular to the axis, it is also
effacing the rugose folds characteristic of the lining of the empty
bladder. The net effect of these actions is to make the back wall a
better reflector as the bladder distends.
There are two other mechanisms having an effect on the echo return
at higher volume levels which have now come to light as a result of
the present invention. At any acoustic interface, some portion of
the incident wave will be reflected and some will pass through.
This is true of the back wall of the bladder, particularly at the
higher levels of distention. The insonating beam passes through a
greater distance of the low attenuation urine than formerly, and
the back wall has become a better target. Some portion of the
energy will penetrate the back wall and produce reflections from
the muscle layers surrounding the bladder. In addition, the
distended bladder is now pressing against the organs and blood
vessels that surround it.
Movements and pulsations in these organs are impressed on the wall
of the bladder. The net effect of these two conditions is to cause
an apparent increase in the duration of the back wall echo, which
is related to increasing distention.
The difference between the present invention and previous "A" scan
technology is that the resident software algorithm keeps track of
all of the variables, assigns weighted values to them, depending on
their relative information content, and then derives a discrete
numerical value for the perceived volume in each scan. That value
is put into memory and the trend of the value is periodically time
averaged, with that resultant both saved and made available for
display.
By fully exploiting not just the location of the bladder wall, but
also the information extractable from the changing signature of the
wall echoes, the range of volumes through which the relative
bladder distention can be tracked is substantially enhanced.
As is understood by those of skill in the art from the foregoing,
rapid quantification of the relative distention of the bladder of a
human subject is achieved according to the present invention by
transmitting an acoustic wave into the bladder of the human subject
so as to create a reflected acoustic waveform: measuring a time
range together with an energy level of the reflected acoustic
waveform: applying a signal processing algorithm thereto; and
comparing the resulting measurement against a selectable
standard.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention,
including its objects and benefits, reference should be made to the
detailed description, which is set forth below. This detailed
description should be read together with the accompanying drawings,
wherein:
FIG. 1 is a functional block diagram of a preferred embodiment of
the present invention,
FIGS. 2(a), (b), (c) is a three-part diagram showing in simplified
graphic form the acoustic beam path interaction with an empty
bladder: a rendering of the oscilloscope presentation of the
amplified and detected output resulting from that interaction; and
the same waveform in digitized format, respectively:
FIGS. 3(a), (b), (c) is a three-part diagram in the same format as
FIG. 2, but with the bladder in a partially distended state;
FIGS. 4(a), (b), (c) is a three-part diagram in the same format as
FIGS. 2 and 3, but with the bladder in a well-distended state;
FIG. 5(a) is an amplitude histogram of a discrete digitized echo
waveform;
FIG. 5(b) is a graphical illustration of a time/weighting curve
applied to the date in FIG. 5(a):
FIG. 5(c) is the resulting weighted histogram which will be
processed by an algorithm to give a numerical equivalent; and
FIG. 6 shows the progression of a typical data trend line versus
desired volume for alarm activation.
DETAILED DESCRIPTION OF THE INVENTION
The block diagram in FIG. 1 illustrates a preferred embodiment of
the device according to the present invention. The system is under
the control of microprocessor 4, with all programming stored in a
64K EPROM 6A,B. At turn on, read gate 14 is enabled and the status
of the two BCD switches 15A,B is determined. Switch 15A sets the
desired volume level at which an alarm is to be sounded. Switch 15B
selects the operating mode of the system and the display status.
The microprocessor 4 then sends the first command to pulse. This
pulse activates power amplifier 3A which drives transducer element
1. The piezoelectric transducer element produces a burst of 0.5 MHz
sound waves when the 300 nano-second, 12-volt DC pulse is applied
to it. This is the transmit portion of the scan, which lasts for
approximately 40-microseconds including the pulse decay time. The
system then goes into a listening mode for approximately
250-microseconds. The receiver 3B consists of an input differential
amplifier; and absolute value detector, and an output gain block.
The output of the receiver is limited to a swing between 0 and
.+-.5 volts. Any returning echo is amplified, conditioned, and
applied to the input of analog-to-digital converter 5. The
converter is enabled by the same command to pulse as the power
amplifier. Since the receiver "sees" the transmitted pulse as well
as the echo, the first 40-microseconds after T.sub.O is ignored.
This prevents the transmitted pulse from creating an error
artifact. Starting after the end of the transmit pulse, the A-D
converter 5 performs 128 successive quantizations, each occupying a
time block of 1.7 microsecond. The depth into the abdomen of
patient 2 insonated in this length of time has proven, in all of
the test cases to date, to be sufficient to view the back wall of
bladder 16.
The echo return contains some amount of low level noise, which can
be removed by thresholding. Short term pulsations (usual duration
approximately 1/2 second) that appear to be caused by peristaltic
action in the intestines, are removed by time averaging. Because
the amount of intestinal overlay of the bladder and the resident
ambient noise is quite variable between individuals--with children
so far tending to give cleaner returns than adults--the number of
scans to be averaged, their spacing and the update rate can all be
varied to suit the user. Between active cycles, power control 18A
is employed to maximize the life of battery 18B. In the current
configuration (which was optimized for a test population of adult
males) four individual pulse-echo scans are taken and processed at
eight millisecond intervals, the results are averaged, the
weighting algorithm is performed, and the results thereof placed
into data memory 6B. Four seconds later another group of four scans
is taken, processed, averaged and placed into data memory 6B. This
procedure is repeated four times. After the fourth iteration, the
results of the entire group are averaged, the output of display 17
is updated, and the numerical value is compared to the value of the
desired alarm volume level. If the currently perceived volume value
meets or exceeds the desired level, then the selected alarm alarms
are activated. In order to accommodate the varying needs of the
individual users, both the type and the duration of the alarm are
switch selectable. The alarm suite is comprised of visual 8,
tactile 9, and audio 7 (volume is also adjustable), and remote 10.
Alarm duration is adjustable from one second to eight seconds in
one second increments.
In actual practice, the setup and utilization of the device of the
present invention is straightforward. The individual under test is
allowed to accumulate some quantity of urine in the bladder by
simply drinking a fluid and waiting approximately thirty minutes.
The transducer 1 with a suitable couplant is applied to the abdomen
of subject 2 in the area just above the pubic hair. The transducer
1 is then moved around to obtain a maximum reading on display 17
with the device set to pulse continuously. This is taken to be an
indication that bladder 16 is in the view of the insonating beam,
as an empty bladder or a misaligned beam will afford very low
numerical values. The (arbitrary) numerical range shown on display
17 has typically varied in the test population from a value of
8-10--representing an essentially empty bladder--up to a reading of
55-65--representing volumes in excess of 500 cc. Alarm level switch
15A permits the selection of sixteen levels ranging from 9-57. This
is an arbitrary range based on the statistics of the test
population who tended to void between values of twenty-four, which
typically gave volumes of 240-260 cc, and forty-two, which gave
volumes of approximately 400 cc. The transducer 1 is secured to
patient 2 by an elastic belt, similar in construction to a hernia
truss belt. The electronics package, including power control 18A
and battery 18B, is carried in a case on a shoulder strap.
In practice, with the device being worn by an individual for an
extended period of time who is going through the normal daily
routines, some operational characteristics were noted. When a
normal, functioning individual accumulates some volume in his/her
bladder, the physiological sensation is not constant. When the
feeling of need to urinate is first apparent, it comes and goes,
and the individual can be distracted. As the volume of urine
increases, however, so does the frequency and urgency of the
sensations, until such point as the individual feels substantial
discomfort, which may be distracting from the task at hand, and
he/she decides to void. Throughout, there are strains and postures
that increase the physiological sensations. These are, however,
transitory until the volume of urine becomes excessive.
The present invention mimics the type of progression set forth
above. Since it is reasonable to assume that the individual will
want to accumulate an appreciable volume of urine in the bladder
before taking the time to void, an intermediate alarm level was
selected for the test program. It was noted that when the bladder
is empty, or when it has a very small amount of urine therein, body
movement did not produce any false alarms. When some amount of
urine (80-100C ) is present in the bladder, however, then body
movement can produce an occasional, transitory alarm. When such
movement ceases, the alarm stops. Of course, the individual could
choose to void at this time, but, as is usually the case with
normal perception, the individual does not choose to void at the
first sensation. Rather, as time goes on and the alarm trigger
level is approached, the alarm (again as with the natural
sensation) becomes more and more frequent, until they are annoying.
The individual, or the individual's caretaker can over a period of
time adjust the alarm level to that point which works best for the
individual involved eliminating false positives for certain
individual.
To better understand the function and operation of the invention,
it is necessary to examine the acoustic wave interaction with the
bladder as is shown in FIGS. 2-4. In FIGS. 2(a-c), the bladder is
essentially empty. In FIGS. 3(a-c), the bladder is being filled,
and in FIGS. 4(a-c)the bladder is at maximum fullness. In each of
FIGS. 2-4 are simplified, illustrative diagrams of the physical
bladder and the ultrasonic transducer (A), a conventional
ultrasonic signal S showing the electrical radio frequency (RF)
wave forms obtained from the transducer after conversion in the
receiver(B), and the energy wave forms E (C). Each of FIGS. 2-4
shows the tissue/transducer interface 11, the bladder front wall
12, and the bladder rear wall 13.
In FIG. 2, with the bladder essentially empty, transducer 1 is
placed on the patient with a conventional couplant for ultrasound.
The sound wave excited by the pulser/receiver 3 of FIG. 1 causes
the ultrasonic signal shown in FIG. 2, diagram 2B, time position
11. The wave also reflects off the bladder front wall 12 and the
bladder rear wall 13, with the resulting ultrasonic signals 12 and
13, respectively, in diagram 2B. The bottom diagram 2C in FIG. 2 is
the ultrasonic energy with its corresponding signals 11, 12, and
13. These signals are obtained by adding the absolute amplitude of
the RF wave forms for each pulse and averaging the resulting
summation over N cycles of the measurement, in accord with the
value weighting function by the programmed algorithm.
In FIG. 3, with the bladder partially full, the bladder has
inflated as shown in diagram 3A of the figure, and the RF waveforms
have changed as the bladder shape has changed. In particular, the
rear wall reflection has moved back in time, and additional
reverberation has built up in the rear wall signal as shown in 3B,
wave 3 as well as in 3C, wave 3.
In FIG. 4, with the bladder substantially full, the change in shape
has continued, although the rear wall 13 has not moved in a simple
fashion during filling. The energy seen in the rear wall
reflection, however, continued to increase as the bladder was being
filled. In fact, for a bladder filling past about 60% fullness, the
rear wall hardly moves at all, while the energy reverberation at
the rear wall continues to increase. Thus, it can be seen that a
monitor of the rear wall position only would not be accurate during
critical near-full periods. In sharp contrast thereto, this
invention, which measures the energy in the rear wall reflection as
well as the rear wall position, is accurate as a monitor for the
entire range of bladder fullness.
FIGS. 5 and 6 relate to the internal components of this invention
and their function in more detail. The converter 5 and the memory 6
actually act as a signal averager, taking the digitizer output and
multiplying it by some weighting function related to bin number,
while checking that the signal falls in the correct time range or
bin number (J). The entire operation is controlled by the software
to configure the function and the mathematical operations for the
specific subject.
As the simplest case, the function used is the sum of energy
amplitudes in bins (J-K.+-.W) that correspond to the rear wall and
beyond of the bladder, where W is the width of the reverberation
signal at the rear wall. A check on the data quality is that bins
less than (J-K) show no significant amplitude. Such a lack of
signal corresponds to the fact that when the bladder contains
water, the path length between the front and rear walls should show
no scattering, i.e., a simple water path exists.
The internal logic calculation of FIG. 6 shows the result of a
typical bladder during filling. The function has been adapted to
the specific subject so that the F(J,E) and the alarm threshold
correspond to the best time for that subject to be notified to
urinate.
A complete electronics package is worn by the subject with the
transducer positioned by means of a flexible mounting belt. The
electronics package advantageously contains means to alert the
subject with any or any combination of a variety of stimuli
including a tactile alarm (e.g., a vibrator), a visual alarm (e.g.,
an LED mounted on eyeglasses), an audible alarm (e.g., a buzzer),
and a remote alarm (an RF link to a receiver monitor). In addition,
the electronics package advantageously contains a working mode
which lets the package work in a "sleep" configuration when the
bladder should be empty (after successful elimination). In that
mode, the frequency of pulses and measurements is reduced to
lengthen the life of the power supply (which is advantageously a
battery) in the package. Moreover, parameters governing the user's
interaction with the device, such as typical void volume and alarm
preference, are entered by the user or his/her caregiver into the
logic system externally by adjusting controls on the face of the
microprocessor. This affords a customization for each individual
and a quick and simple modification of existing parameters at any
time. The user or his/her caretaker is accordingly allowed to
select the level of bladder fullness at which he/she would like the
alarm to sound.
As is understood by those of skill in the art, the ultrasonic
transducer, pulser/receiver, analog-to-digital converter, program
and data memory, audible alarm, visual alarm, tactile alarm, and
remote alarm employed herein are per se well-known, and therefore
are not disclosed in detail herein.
The preferred embodiment of the invention disclosed hereinabove
relates to the propagation of ultrasonic energy and averaging the
energy signals over a number of measurement cycles to rapidly
quantify the relative distention of the bladder of a human subject.
Moreover, the programming of specific functions of the particular
subject into the logic system permits a fine tuning which affords
accurate operation with a wide variety of subjects and
conditions.
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